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Hump Zoology in CVs
as seen by CBA zookeepers
taken from:
Appendix A, The 2001 Superoutburst of WZ
Sagittae
[nicely-formatted version of this table
(PDF)]
in this HTML version of the table below,
w is equivalent to the
lower-case Greek omega;
W to the upper-case Greek omega
1. Orbital Hump ·
2. Outburst Orbital Hump ·
3. Common Superhump
4. Late Superhump ·
5. Positive Superhump ·
6. Apsidal Superhump
7. Negative Superhump ·
8. Nodal Superhump ·
9. Permanent Superhump
10. Quiescent Superhump ·
11. Superhumper ·
Notes
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Type:
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1. Orbital Hump
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Meaning:
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Signal at the orbital frequency wo in quiescence.
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Example Stars:
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U Gem, WZ Sge
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Alleged Origin:
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Presentation effect of hot spot (stream-disk impact region).
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Type:
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2. Outburst Orbital Hump
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Meaning:
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Signal at or very near wo in outburst. Quite
rare; appears to be transiently present in a few SU UMa stars (possibly
restricted to the WZ Sge class) in the earliest stage of
outburst. Sometimes also called early, immature, and orbital
superhumps; but we prefer to restrict "superhump" to cases where the
frequency is distinct from wo.
| | Example Stars:
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WZ Sge, AL Com
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Alleged Origin:
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Unknown.
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Type:
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3. Common Superhump
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Meaning:
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Signal at wo-W, shown by all SU UMa stars in
outburst; decays roughly on a timescale of 1-3 weeks. Often of very large
amplitude (0.4 mag), and thus a major element in the outburst energy
budget. So universal and so extensively studied that "superhump",
sans qualifier, often implies a common superhump.
| | Example Stars:
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SU UMa, VW Hyi, 54 others
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Alleged Origin:
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Periodic tidal disturbance of the disk by the orbiting secondary (thus
requiring a slow apsidal advance to match the frequency shift to
wo-W).
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Type:
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4. Late Superhump
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Meaning:
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Signal at wo-W, sometimes following (3) and
basically defined by a sudden phase shift in (3) of ~0.5 cycles, with
little or no change in period.
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Example Stars:
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OY Car, VY Hyi
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Alleged Origin:
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Not securely known, but definitely similar to (3) - features apsidal
advance of an "elliptical" disk.
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Type:
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5. Positive Superhump
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Meaning:
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A general term for any signal with P slightly exceeding
Po (a small positive increment in period) and hence
w=wo-W. Includes all common superhumps.
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Example Stars:
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77 CVs
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Alleged Origin:
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Just an observational term.
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Type:
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6. Apsidal Superhump
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Meaning:
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Alternate to (5), if you subscribe to the theory that (5) arises from
apsidal advance ("precession") of the disk, in which case W is the
precession frequency. Includes all common superhumps, if you buy that
theory.
| | Example Stars:
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77 CVs, probably
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Alleged Origin:
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Probably the same as (3) or (4).
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Type:
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7. Negative Superhump
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Meaning:
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A general term for any signal with P slightly less than
Po (a small negative increment in period) and hence
w=wo+N.
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Example Stars:
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V503 Cyg, TV Col, V603 Aql
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Alleged Origin:
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Just an observational term.
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Type:
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8. Nodal Superhump
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Meaning:
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Alternate to (7), if you subscribe to the theory that (7) arises from
nodal precession (wobble) of the disk, in which case N is the
precession frequency.
| | Example Stars:
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same, probably
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Alleged Origin:
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Not securely known.
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Type:
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9. Permanent Superhump
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Meaning:
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Any positive or negative superhump which is long-lived (months or
longer) and not associated with eruption.
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Example Stars:
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AM CVn, V603 Aql, BK Lyn
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Alleged Origin:
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Probably same as (3), (4), and (8).
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Type:
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10. Quiescent Superhump
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Meaning:
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Extremely rare, and not a term in general use. A superhump in states of
very low luminosity, with no connection yet established to the other
superhump types.
| | Example Stars:
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AL Com, CP Eri
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Alleged Origin:
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Unknown.
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Type:
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11. Superhumper
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Meaning:
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A star which engages in superhumps.
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Notes
(a) "Outburst" here means superoutburst. Happily, we still
know of no related periodic signals characteristic of normal outburst.
(b) It may well be true that all apsidal precession is prograde
(giving a positive superhump) and all nodal precession is retrograde
(giving a negative superhump). The limited data available now are
consistent with this. If counterexamples are found, these definitions
would be affected somewhat.
(c) Superhumps can be characterized by 3 fundamental frequencies
(wo, W, N), and the
dominant signal is nearly always wo-W or wo+N. But studies of high sensitivity and
frequency resolution often reveal components with w=nwo-mW (where n=any small integer
and m=1, 2, ..., n) or nwo+N (same terminology). We consider
these as "fine structure" and thus outside this classification effort.
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